Since the advent of a resist for KrF excimer laser (248 nm), an image forming method called chemical amplification is used as an image forming method for a resist so as to compensate for sensitivity reduction caused by light absorption. For example, the image forming method by positive chemical amplification is an image forming method of decomposing an acid generator in the exposed area upon exposure to produce an acid, changing an alkali-insoluble group into an alkali-soluble group by using the generated acid as a reaction catalyst in the baking after exposure (PEB: Post Exposure Bake), and removing the exposed area by alkali development. A positive image forming method utilizing this chemical amplification mechanism is now the mainstream.
Also, there is known a so-called immersion method of filling the space between the projection lens and the sample with a high refractive-index liquid (hereinafter sometimes referred to as an “immersion liquid”) in an effort to more shorten the wavelength and thereby realize high resolution. For example, JP-A-2008-268933 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) describes a case where a resin having a specific acid-decomposable repeating unit and a specific resin free from a fluorine atom and a silicon atom are incorporated into a positive resist composition and the followability of immersion liquid is thereby improved.
However, in the above-described positive image forming method, an isolated line or dot pattern can be successfully formed, but in the case of forming an isolated space or fine hole pattern, the pattern profile is liable to be deteriorated.
To meet the requirement for finer pattern formation, as well as the currently mainstream positive pattern, there is recently known a technique of resolving a resist film made of a chemical amplification resist composition by using an organic developer to form a negative pattern. As such a technique, for example, in a method for forming a negative pattern by using an organic developer and an immersion method, a technique of adding a resin containing a silicon atom or a fluorine atom is known (see, for example, JP-A-2008-309879).